Safety device



June 19, 1934. D HOFFMAN 1,963,701

SAFETY DEVICE Filed Dec. 28, 1931 3 Sheets-Sheet l lnvenlor ,jaroz EZfa/ 1mm June 19, 1934. D. E. HOFFMAN 1,963,701

SAFETY DEVICE Filed Dec. 28, 1931 3 Sheets-Sheet 2 flllorney D. E. HOFFMAN SAFETY DEVICE June 19, 1934.

Filed Dec. 28, 1931 3 Sheets-Sheet 3 wan.

flllomcy Patented June 19, 1934 UNITED STATES PATENT OFFICE 2 Claims.

This invention appertains to new and useful improvements in safety devices and especially adapted for use in polyphase augmenting electric v V current circuits, and the principal object of the r invention is to provide a safety device in the nature of a relay for interrupting the polyphase circuit in the event a break occurs in one or more of the lines of the circuit. Another important object of the invention is to provide a safety device for interrupting a polyphase circuit in the event an unbalance occurs, as when the current or potentials of polyphase system circuit becomes so unbalanced in the direction of one or more of the lines of the system It as to make further operation of a motor or other electrical machine undesired, to save the machine from damage by overheating.

A further object of the invention is to provide an improved phase balanced relay for polyphase alternating electric current systems, such that over current conditions similarly aflecting all the phases will not cause an operation of the relay. Another important object of the invention is 26-to provide a relay of the character stated which will be substantially fool-proof and constructed in such a manner as to make the parts thereof accessible for the purpose of repair or replacement.

invention will become apparent to the reader of the following specification.

In the drawings:-

Figure 1 represents a top plan view of the re- 85 lay.

Fig. 2 represents a sectional view taken substantially on line 2-2 of Fig. 1.

Fig. 3 represents a side elevational view of one of the cores or armatures. Fig. 4 represents a vertical sectional view through one of the adjusting nuts for the armatures.

Fig. 5 represents a top plan view of the spider.

Fig. 6 represents a top plan view of the rocker arm.

Fig. 7 represents a fragmentary side elevational view of the switch and contact spring.

Fig. 8 represents a side elevational view of the post.

Fig. 9 represents an upper end elevational view of the post.

Fig. 10 represents an enlarged sectional view taken substantially on line 1010 of Fig. 8.

Fig. 11 represents a fragmentary sectional Other important objects and advantages of the view taken substantially on line 11-11 of Fig. 12.

Fig. 12 represents a fragmentary detailed sectional view taken substantially on the same line as Fig. 2 and showing the switch in open posi- 6 tion.

Fig. 13 represents a diagrammatic view disclosing the present invention hooked up with an automatic starter and showing the alarm circuit.

Referring to the drawings wherein like nu- C5 merals designate like parts, it can be seen in Fig. 13 that numerals 5, 6 and 7 represent the lines of a polyphase circuit from which leads 8, 9 and 10 can extend at various points to various polyphase motors. Numeral 11 represents a partic- 7C ular motor to be protected by the safety device, while numeral 12 generally refers to an automatic starter box mechanism, the operation of which is very well known to those skilled in this particular art. 7 5- In association with this starter is the thermostatic, switch 13 and the float controlled switch 14, the latter being employed especially in mines where the motoi's are used in conjunction with hydraulic pumps.

A novel relay is generally referred to by numeral 15 in Fig. 13 and is interposed between the starter 12 and the motor 11 to be protected, and a detailed description of the same will now be given;

The relay includes the di-electric base 16 preferably of a rectangular shape to conserve material the same being provided in upstanding position at the three corners thereof with magnetic coils 17, 18 and 19. An armature or core 20 is vertically slidable in each of these coils 17, 18 and 19, and each of these armatures 20 has an upstanding stem 21 thereon projecting from an eccentric position at the upper end of the armature and being threaded as at 22 to permit 95 engagement therewith of a nut 23, each of the said nuts being provided with 2. depending and pointed leg 24.

As is apparent in Fig. 1, these coils 1'7, 18 and 19 are arranged at 120 intervals on the base 16, and an upstanding post 25 is provided at the center of the base 16 and is secured to the same by a screw 26. This post 25 is provided with a block 27 extending therethrough at its intermediate portion, and extending upwardly through the post 25 from this block 27 is a bore 28 opening through the upper end of the post, while additional bore 29 extends from the block 2'7 downwardly in the post 25.

The upper end of the rod 30 projects upwardly through the opening 31 centrally on the threelegged spider 32 and has its upper end threaded into the substantially triangular shaped plate 33 which has rollers 34 mounted at the ends thereof. Three pins 35 are suitably secured to the central portion of the spider 32 about the opening 31 and extend below the same to bear into the recesses 36 in the upper end or" the post 25. The post 25 is beveled at points 37 between the recesses 36 to permit the spider 32 to easily rock in response to the action of the armature 20 by the coils aforementioned.

Numeral 38 represents a di-electric rocker arm which is bifurcated at one end to receive the brace bar 39, the arm 28 being pivotally connected to the bar 39 as at 40. The opposite end of the arm 38 is provided with a cap 42 having a small finger 43 projecting therefrom and defining a recessed shoulder 44 which is capable of abutting the shoulder 45 which is supported by the leaf spring contactor 46, the latter being secured as at 47 to the base 16. Immediately above the shoulder 45 the leaf spring contactor 46 is provided with an opening 46 which. is capable of receiving the cap 42 on the same is elevated by the unbalanced energization of the coils 1'7, 18 and 19.

Numeral 49 represents a contact post, having a contact 50 at its upper end and a pawl tube 51 is threaded through the lower portion thereof to form a guide for the pull cord 52, the same being attached as at 53 to the leaf spring contactor 46, the tendency of the spring 46 being to move inwardly and engage the contacts 54.

The connection between the polyphase circuit and the automatic starter is accomplished through the contacts 50 and 46 and when the switch is in the position shown in Fig. 2, the system is in operative order.

It can be seen, that the rod 30 extends downwardly from the plate 33 to pass through the opening 55, where a spider with an opening to receive the cross pin 56 for supporting the arm 38. Below this point, the rod 30 is provided with a reduced portion 57 which snugly engages in the small bore 29. The signal contact 54 is located on the di-electric block 58 which is carried by the upper end of. the post 25. (See Fig. 8). As is clearly shown Fig. 11, it can be seen that the rod 30 is reduced for plane surfaces for relatively snug disposition through the opening and also to divide the shoulders 59 against which the arm 38 can abut.

In operation, it can be seen, that the parts are normally in the position shown in Figs. 1 and 2 when the circuit is in working order. However in the event one of the lines of the polyphase circuit becomes broken, there is an unbalancing of the relay. obviously results in the de-energization of one of the coils 1'7, 18 or 19 and as there are two coils energizing, the function of these coils will be to overbalance the deenergized coil by attracting their armatures 20 and tilting the spiders 32.

so as to disengage the shoulder 44 from the roller 45 on the spring contactor 46, permitting the shoulder and finger to pass into the opening 48 of the spring contactor 46 while the spring contactor 46 flexes inwardly to engage the signal contact 54, thus breaking the connection to the automatic starter, disrupting the energization of the motor 11 and closing the alarm circuit 60 including the lamp or other signal means 61, when the contactor 46 actually engages the contact 54.

In ordinary increase and decrease of current values there is no effect on the relay as it is perfectly balanced in the polyphase circuit and each of the coils accepts its proportions of the values, and it is only when one of the lines breaks or otherwise becomes impaired to render one of the coils 17, 18 or 19 de-energized, that the relay will operate to interrupt the operation of the motor 11 or any other motors that are to be protected by this device.

In the event there is a natural unbalanced condition of the polyphase system, the armatures 20 can be adjusted by feeding the nuts 23 in the proper direction to vary the position of the armatures properly with respect to their corresponding coils.

It will be observed, that the outer end of each of the legs of the spider 32 is provided with a recess 61 for receiving the pointed end of the corresponding leg 24 and this to the end, that the nut will not self-adjust itself. Obviously, this novel relay may be used in instances where the voltage would be too high to permit its passage through the device in which event, the current can be taken by way of step-down transformers. Furthermore this device can be used in conjunction with phase-wound motors which employ slip ring brushes which in operation frequently break connections and if not noticed in time, is very apt to result in serious damage to the machine.

While the foregoing specification sets forth the invention in specific terms, it is to be understood that numerous changes in the shape, size and materials may be resorted to without departing from the spirit and scope of the invention as claimed hereinafter.

Having thus described my invention, what I claim as new is:-

1. A safety device of the character described comprising a plurality of solenoids, a tiltable spider connected to the armatures of the solenoids, a switch including a stationary contact, and a leaf spring contact tensioned away from the stationary contact, a trip member for normally maintaining the leaf spring contact engaged with the stationary contact, and means between the trip member and the spider whereby the rocking action of the spider will release the said trip member said means including antifrictional members to ease the action of the spider against said means.

2. A safety device of the character described comprising a plurality of solenoids arranged on the line of an imaginary circle, a vertical slidable pin mounted substantially centrally of said solenoids, each of said solenoids having a movable core, a spider connected to one end of each core, said spider having an opening therein to receive the said pin, and through which the pin is slidable, switch means, a trip for the switch means, said pin being operative to release said trip, the upper end of the said pin being provided with a plate against which the spider is rockable, and a fulcrum for the said spider.

DORSEY E. HOFFMAN. 

